The excitatory amino acid (EAA) neurotransmitters, such as glutamate and aspartate, have been implicated in the pathology of a number of neurological disorders, including epilepsy, stroke/anoxia, and neurodegenerative diseases such as Huntington's and Alzheimer's Diseases and amyotrophic lateral sclerosis. Drugs which antagonize EAA neurotransmission offer a novel approach to treating these disorders. The goal of this project is to isolate novel and specific glutamate receptor antagonists from previously uncharacterized spider venoms. Spiders have recently attracted attention as a good potential source of therapeutically useful EAA receptor antagonists because their venoms contain antagonists of the glutamate receptor of the neuromuscular junction of their insect prey. Indeed, previous studies, including our own preliminary results, suggest that many spider venoms do contain antagonists of mammalian EAA receptors. In phase I, six spider venoms will be fractionated by HPLC and screened for neuroactive components using two independent methods: a spinal reflex assay, and receptor binding assays. Next, the mechanism of action of the active components will be determined using more specific electrophysiological and receptor binding assays as well as an in vitro excitotoxicity assay. Finally we will perform preliminary structure analyses of those compounds which appear to be EAA receptor antagonists. In phase II, the complete chemical structure and chemical synthesis route of promising compounds will be determined, and further studies of their in vivo efficacy, toxic effects and bioavailability will be performed.